There are large areas of the world in which fresh water is in critical demand. Many different methods are being utilized to recover fresh water from salt or brackish water. These methods necessarily produce a salt brine or a solid residue of salts which may provide a waste disposal problem.
In the past, water vapor has been removed from humid air primarily for the purpose of lowering humidity. This humidity lowering has been accomplished chemically and mechanically. When done chemically, using chemicals to absorb water from the atmosphere, the water is then not readily available for further usage as potable water. In the usual mechanical de-humidifying processes, as conducted in commercial de-humidifier units, the atmosphere is passed over cooling coils through which a refrigerant is passed.
In recent years, it is becoming more usual for people in both offices and homes to drink bottled water rather than water from the tap. Countless other situations exist where water is difficult to obtain or where available water or water quality leaves much to be desired. In many cases, this also creates a need to carry and lift heavy bottles of water periodically and to carry the water from the place where it was purchased to the place where it will be used.